External HD recognized-no partition

I have an external Hitachi HD. My system is recognizing the hardware, but when I try to save to the drive, this is the message: Folder is not accessible, the folder may be located in an unavailable location, prtected with a password or the file name contains a/or\.

I went into Disk Management and saw there was no "F" Drive Partitioned, which was at one time. Went to My Computer, pulled up the F Drive, and there are no files. So, I formated the drive. However, I really don't think it formatted, because Windows cannot see the file.

Please, I need sound advice. I need this hard drive for school coming up. I do not know why this is not functional. It was fine the last time I used it...about 8 months ago. That was when I noticed something was wrong when the docs would not save to the F drive. Didn't think anything of it, I just saved to my C drive. Now my C drive is almost full. I need the the HD for Adobe CS5.

As a first test on your external drive, does it have a 'power on' light, also when you plug it in to the USB socket on PC, put your hand flat on the case, can you tell if it's spinning up inside? ( I can hear my Seagate, 2 clicks then drive motor speeding up.)
Try a different USB socket on your PC if you have a choice. If you are using a tower PC, use the USB sockets on the back, rather than the front panel.
Assuming it is working, In 'Computer', does the drive appear on the top row to the right of 'C' ?
If you right click on it, and choose properties, does the pie chart show saved content on the disk? (ie, part pink/ part blue).
If you have a Flash memory stick, does that appear in 'Computer' when plugged in?
>>(all this is to prove if the drive is actually working)
If all the above is true, and drive seems to be working, can you go into 'Control Panel', 'Hardware and sound',' Device manager','Disc drives'
right-click and choose; 'Scan for hardware changes'. Click on the small white arrow left of 'Disc Drives'.
Can you see your Hitachi drive at the bottom of the list?